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1. Field of Invention
The invention is a mechanical suspension system for cab-over tractors, specifically those used in terminal transport of semi-trailers having two front cushion dual suspension components on the front pivot area of the cab to tractor frame connection and a single rear cushion dual suspension component on the rear of the tractor frame at the cab-over latch area, the three point dual suspension system providing a more stable suspension package than the four point and other currently available suspension systems.
2. Description of Prior Art
The following United States patents are disclosed herein and incorporated into this application for utility patent. All relate to suspension systems for heavy duty trucks or trains. A primary application for this current invention is for terminal tractors as disclosed in the brochure attached to the Form 1449, from Crane Carrier Company, or CCC(copyright).
A suspension system for a vehicle cab including springs and a sway resisting torsion bar is disclosed in U.S. Pat. No. 6,073,714 to McHorse, et al. which is provided to minimize lateral sway of the cab, primarily through use of a bushing or a singular spring and the torsion bar. A combination spring/shock absorber is disclosed in U.S. Pat. No. 5,590,733 to Ljungholm, et al. in which four shock absorbers with external springs are provided to cushion the cab of a tractor truck, also employing a second shock absorber on a lateral arm for diagonal reinforcement and suspension. A vibration dampening shock absorber is disclosed in U.S. Pat. No. 5,253,853 to Conaway, et al.
A two stage dampening shock absorber is disclosed in U.S. Pat. No. 5,249,652 to Leitzman, et al., which provides a primary force dampener with a second, stronger force dampener within the single shock absorber. U.S. Pat. No. 5,209,316 to Bauer and U.S. Pat. No. 4,871,189 to Van Breemen both disclose suspension systems using air springs, an air reservoir, shock absorbers and height control valves. A dual spring suspension system for railroad cars, having an inner coil spring with an additional stronger outer coil spring is disclosed in U.S. Pat. No. 4,186,914 to Radwill, et al.
The primary objective of the invention is to provide a terminal tractor cab suspension system employing a three point suspension system having each point containing a dual directional suspension system for absorption of both upward and downward forces exerted on the cab.
Most terminal tractors are built with the rear axle mounted directly to the frame, referred to as a xe2x80x9chard tailxe2x80x9d or xe2x80x9csolid mountxe2x80x9d which indicates the lack of a flexible rear suspension system on the chassis. These vehicles are known to create a hard ride with operator discomfort and maintenance cost increase to the vehicle. Rough terrain transfers shock loading to the cab causing the cabin to pitch, roll and backslap the driver throughout operation.
The industry standard four point mounting system has two front mounts allowing the cabs to tilt forward for maintenance. This prior art is shown in FIGS. 1 and 2 of the drawings. They are typically rubber bushings enclosed in steel sleeves with cap screws or pins inserted through the canters of the bushings to create the pivot point. Very limited movement is obtained by the rubber bushings and achieve less than xc2xc inch movement relative to the chassis. Virtually all pitch and roll movement of the chassis is transferred to the cab, causing the cabin to be thrown at every bump.
The rear mounts of the four point mounting system are rubber pads, cushions or rubber dock bumpers at both frame rails under the rear of the cab. They too are stiff and apply less than xc2xc inch deflection to cushion the ride. The cab bucks up and forward every time a bump is hit and the constant pitch, roll, bump and bucking of the cab leads to premature failure of all involved components. Electrical systems fail, connections vibrate loose, terminals crack and separate, lamps burn out or rupture, switches and resistors fail and motor life is shortened.
Major terminal tractor manufacturers have tried for years to develop a rear suspension system that would provide the flexibility to improve ride character and be adaptable for full and empty loading conditions, and durable for high cycle terminal applications. Air suspensions are expensive and difficult to maintain in terminal applications. Additionally, terminal tractor cabs do not adapt well to highway tractor applications because most, if not all, terminal tractors have the offset cab configuration where the majority of the cab is left of center, thus providing an offset balance of the cab design, making the four point system center of gravity not anywhere near the center of gravity of the terminal tractor cab, which is generally nearest the left frame rail. Major imbalances and stresses result from the application of these four point systems to the left set terminal tractor applications.
The current invention employs a three point suspension system, as shown in FIG. 3 of the drawings. The two front mounts pivot to allow the cab to tilt for maintenance. The single rear mount will be located in the most advantageous place to balance the mass of the cab effectively between the three mounts. The center of gravity is approximately located at the operator""s seat, the most neutral location within the cab. No unbalanced forces are applied to the cab using this three point system. This invention addresses the problems of high vertical accelerations and torsional stresses by significant reduction of vertical stresses and some horizontal stresses, by maintaining a more stable static condition of the cab to the tractor frame, by placement of the center of gravity under the operator of the terminal tractor, and by providing an upward and downward suspension system for active operation employing three springs in each single unitxe2x80x94a heavy spring for downward force reduction comprising approximately 90% of the vertical accelerations associated with normal operations, a lighter spring for upward stress reduction and negative accelerations (bucking) and an elastomeric spring for extremely hard forces, comprising about 10% of the forces incurred in normal operation or observed in very poor terrain, each applied between a stainless steel shaft and a steel sleeve operating as a single unit, two units applied to the front of the terminal tractor cab which are pivotal and a third inverted unit applied to the rear of the cab which is detachable for pivoting the cab for maintenance and repair.
The following drawings are submitted with this utility patent application.
FIG. 1 is a drawing of the prior art of a typical terminal tractor with a four point suspension mounting, indicating front and rear cab mount locations.
FIG. 2 is a drawing of the prior art of a typical terminal tractor indicating a typical center of mass of the cab structure.
FIG. 3 is a drawing of the three point suspension mounting of the current invention on a typical terminal tractor, with center mass indicated.
FIGS. 4a and 4b are drawings of a cross section of a rear mount assembly.
FIGS. 5a and 5b are drawings of a cross section of a front mount assembly.
FIG. 6 is a drawing of the top view of the sleeve assembly for both the front suspension assembly and the rear suspension assembly.
FIG. 7 is a drawing of the side view of the sleeve assembly for both the front suspension assembly and the rear suspension assembly.
FIG. 8 is a drawing of the carrier housing assembly on the rear mount assembly.
FIG. 9 is a drawing of the rubber pivot bushing with the steel sleeve on the support shaft for the front mount assembly.
FIG. 10 is a drawing of the detachable latch bar assembly on the support shaft.